I came across this question
Here is my response to it, I just started myself learning SQL recently.
Select a.roll_number , a.name , b.roll_number from student_information a join examination_marks b on a.roll_number = b.roll_number Group by roll_number Having Sum(subject_one.examination_marks + subject_two.examination_marks + subject_three.examination_marks) < 100;
You need not to group by your result since there should be one row in each table for every roll_number. You did the join right. Now just replace group by and having clause with where condition to check whether sum of all three subject’s number is less then 100 or not. If it less then hundred then select roll_number and name.
Select a.roll_number, a.name from student_information a inner join examination_marks b on a.roll_number = b.roll_number where (subject_one + subject_two + subject_three )< 100;